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* [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store)
[not found] <bug-21998-4@http.gcc.gnu.org/bugzilla/>
@ 2012-07-13 8:54 ` rguenth at gcc dot gnu.org
2012-07-13 11:04 ` steven at gcc dot gnu.org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-07-13 8:54 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21998
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |53947
--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-13 08:54:14 UTC ---
Link to vectorizer missed-optimization meta-bug.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store)
[not found] <bug-21998-4@http.gcc.gnu.org/bugzilla/>
2012-07-13 8:54 ` [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store) rguenth at gcc dot gnu.org
@ 2012-07-13 11:04 ` steven at gcc dot gnu.org
2012-07-13 11:29 ` rguenth at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: steven at gcc dot gnu.org @ 2012-07-13 11:04 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21998
Steven Bosscher <steven at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |steven at gcc dot gnu.org
--- Comment #4 from Steven Bosscher <steven at gcc dot gnu.org> 2012-07-13 11:04:13 UTC ---
(In reply to comment #1)
> They are not equivalent to GCC, the first always stores, the second has a
> conditional store.
Just to clarify, 7 years later: To GCC the two procedures are not equivalent.
In the first procedure,
a1[i] = (a1[i] == v1 ? v2 : a1[i]);
expands as:
if (a1[i] == v1)
a1[i] = v2;
else
a1[i] = a1[i];
while the second procedure expands just as-is:
if (a1[i] == v1)
a1[i] = v2;
In the first case, there will always be a store to a1[i], in the second example
this is not the case. Introducing new stores is not allowed, to avoid
introducing data races, see http://gcc.gnu.org/wiki/Atomic/GCCMM/DataRaces.
I'm not sure how GCC should transform the second procedure to allow the loop to
be vectorized.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store)
[not found] <bug-21998-4@http.gcc.gnu.org/bugzilla/>
2012-07-13 8:54 ` [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store) rguenth at gcc dot gnu.org
2012-07-13 11:04 ` steven at gcc dot gnu.org
@ 2012-07-13 11:29 ` rguenth at gcc dot gnu.org
2013-03-27 11:32 ` rguenth at gcc dot gnu.org
2023-08-04 20:36 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-07-13 11:29 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21998
--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-13 11:28:45 UTC ---
We have two related flags here, -ftree-loop-if-convert-stores, and
--param allow-store-data-races. We can adjust the former to honor the
latter if specified and then eventually vectorize this, too.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store)
[not found] <bug-21998-4@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2012-07-13 11:29 ` rguenth at gcc dot gnu.org
@ 2013-03-27 11:32 ` rguenth at gcc dot gnu.org
2023-08-04 20:36 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-03-27 11:32 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21998
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-27 11:32:19 UTC ---
Note that the concern is also that a1 may be mapped to a read-only segment,
so introducing a store data-race may trap. That's probably out of the C99
language standards scope, but the middle-end has to care about this
possibility.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store)
[not found] <bug-21998-4@http.gcc.gnu.org/bugzilla/>
` (3 preceding siblings ...)
2013-03-27 11:32 ` rguenth at gcc dot gnu.org
@ 2023-08-04 20:36 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-08-04 20:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21998
--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
We can vectorize test2 using mask stores ....
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/21998] New: (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't
@ 2005-06-10 13:22 stefaan dot deroeck at gmail dot com
2005-06-19 14:24 ` [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store) pinskia at gcc dot gnu dot org
0 siblings, 1 reply; 6+ messages in thread
From: stefaan dot deroeck at gmail dot com @ 2005-06-10 13:22 UTC (permalink / raw)
To: gcc-bugs
The following two procedures are functionally equivalent, but the first (more
complicated) syntax is vectorized though the second isn't.
typedef int __attribute ((aligned (16))) aint;
void test(aint * __restrict a1, int const v1, int const v2) {
for (int i=0; i<640; ++i)
a1[i] = (a1[i] == v1 ? v2 : a1[i]);
}
void test2(aint * __restrict a1, int const v1, int const v2) {
for (int i=0; i<640; ++i)
if (a1[i] == v1) a1[i] = v2;
}
vecttest.cpp:7: note: === vect_analyze_loop_form ===
vecttest.cpp:7: note: not vectorized: too many BBs in loop.
vecttest.cpp:6: note: bad loop form.
vecttest.cpp:6: note: vectorized 0 loops in function.
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: /esat/alexandria1/sderoeck/src/gcc/main/configure
--prefix=/esat/olympia/install --program-suffix=-cvs --enable-languages=c,c++ :
(reconfigured) /esat/alexandria1/sderoeck/src/gcc/main/configure
--prefix=/esat/olympia/install --program-suffix=-cvs --enable-languages=c,c++ :
(reconfigured) /esat/alexandria1/sderoeck/src/gcc/main/configure
--prefix=/esat/olympia/install --program-suffix=-cvs --enable-languages=c,c++
--no-create --no-recursion : (reconfigured)
/esat/alexandria1/sderoeck/src/gcc/main/configure --prefix=/esat/olympia/install
--program-suffix=-cvs --enable-languages=c,c++ --no-create --no-recursion
Thread model: posix
gcc version 4.1.0 20050610 (experimental)
/esat/olympia/install/libexec/gcc/i686-pc-linux-gnu/4.1.0/cc1plus -quiet -v
-D_GNU_SOURCE vecttest.cpp -quiet -dumpbase vecttest.cpp -march=pentium4
-auxbase-strip vecttest-gcc.s -O9 -version -fverbose-asm -ftree-vectorize
-fdump-tree-vect-details -fdump-tree-vect-stats -o vecttest-gcc.s
-- cut --
GNU C++ version 4.1.0 20050610 (experimental) (i686-pc-linux-gnu)
compiled by GNU C version 3.4.4 (Gentoo 3.4.4, ssp-3.4.4-1.0, pie-8.7.8).
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: 3cb76b13917ca148a15d77c9a1fb678d
--
Summary: (cond ? result1 : result2) is vectorized, where
equivalent if-syntax isn't
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P2
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: stefaan dot deroeck at gmail dot com
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21998
^ permalink raw reply [flat|nested] 6+ messages in thread
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[not found] <bug-21998-4@http.gcc.gnu.org/bugzilla/>
2012-07-13 8:54 ` [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store) rguenth at gcc dot gnu.org
2012-07-13 11:04 ` steven at gcc dot gnu.org
2012-07-13 11:29 ` rguenth at gcc dot gnu.org
2013-03-27 11:32 ` rguenth at gcc dot gnu.org
2023-08-04 20:36 ` pinskia at gcc dot gnu.org
2005-06-10 13:22 [Bug tree-optimization/21998] New: (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't stefaan dot deroeck at gmail dot com
2005-06-19 14:24 ` [Bug tree-optimization/21998] (cond ? result1 : result2) is vectorized, where equivalent if-syntax isn't (store) pinskia at gcc dot gnu dot org
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